An out-of-the-box Github Mirror for Cloudflare Workers.

worker.js

addEventListener('fetch', event => {
    event.respondWith(fetchAndApply(event.request));
})

async function fetchAndApply(request) {
    let url = new URL(request.url);
    url.protocol = 'https:';

    let new_request_headers = new Headers(request.headers);
    new_request_headers.set('Host', url.hostname);
    new_request_headers.set('Referer', url.hostname);
    let original_response = await fetch(url.href.replace(url.hostname, 'github.com'), {
        method: request.method,
        headers: new_request_headers
    })

    let original_response_clone = original_response.clone();
    let original_text = null;
    let new_response_headers = new Headers(original_response.headers);

    new_response_headers.set('access-control-allow-origin', '*');
    new_response_headers.set('access-control-allow-credentials', 'true');
    new_response_headers.delete('content-security-policy');
    new_response_headers.delete('content-security-policy-report-only');
    new_response_headers.delete('clear-site-data');

    const content_type = new_response_headers.get('content-type');
    if (content_type.includes('text/html')) {
        original_text = (await original_response_clone.text()).replaceAll('https://github.com', 'https://' + url.hostname);
    } else {
        original_text = original_response_clone.body
    }

    return new Response(original_text, {
        status: original_response.status,
        headers: new_response_headers
    });
}